Conjugated Polymers Based on Phenothiazine and Fluorene in Light-Emitting Diodes and Field Effect Transistors

Abstract

Poly[10-(2‘-ethylhexyl)-phenothiazine-3,7-diyl] (PPTZ), poly[9,9-bis(2‘-ethylhexyl)fluorene-2,7-diyl] (PBEHF), and their random copolymers, poly(BEHF-co-PTZ), were synthesized through Ni(0)-mediated polymerization. Light-emitting devices were fabricated using these polymers in an ITO (indium tin oxide)/PEDOT:PSS/polymer/Ca/Al configuration. Each EL device constructed with a poly(BEHF-co-PTZ) copolymer exhibited significantly enhanced efficiency and brightness compared to devices constructed from the PPTZ and PBEHF homopolymers. The EL device constructed with poly(88BEHF-co-12PTZ) exhibited the highest power efficiency and brightness (4200 cd/m2 and 2.08 cd/A respectively). This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arise due to the HOMO levels (∼5.4 eV) of the poly(BEHF-co-PTZ) copolymers, which are lower than that of the PBEHF homopolymer (∼5.8 eV). An organic field effect transistor was also fabricated using PPTZ as a new p-type channel material and characterized. The measured field effect mobility of the transistor was 0.8 × 10-4 cm2/V·s and the on/off ratio of the device was ∼103.

Synthesis and light-emitting properties of new polyfluorene copolymers containing a triphenylamine based hydrazone comonomer

“…The product yield was 5.6 g (81%). 1 Copolymers were synthesized by Ni(0) mediated polymerization with the monomers, BEHF and TPAH according to procedures outlined in the literature [7,8].…”

“…In particular, interest in polyfluorene (PF) derivatives has increased because of their high photoluminescence (PL) quantum efficiency, thermal stability, and also their facile color tunability, which can be obtained by introducing low-band-gap comonomers [7,8]. The poor efficiency of polyfluorene has been improved by blending, copolymerization, and end-capping with charge transporting materials to obtain improved charge injection [9,10].…”

Synthesis of a soluble fulleropyrrolidine derivative for use as an electron acceptor in bulk-heterojunction polymer solar cells

“…Phenothiazine is a well-known electro-active heterocyclic compound and has unique optical and electrical characteristics. The phenothiazine moiety could modify the optical and electronic properties of the fullerene core; in particular, it could raise the LUMO energy level of [60] fullerene [22][23][24]. Moreover, the alkyl group in the phenothiazine moiety could improve the solubility of fullerene in organic solvents, and C 60 -PTZP could improve the morphology of the photoactive layer owing to better phase separation because of its amorphous nature.…”

Synthesis and electroluminescence properties of fluorene–anthracene based copolymers for blue and white emitting diodes

“…Polymer lightemitting diodes (PLEDs), in particular, are widely expected to be the next major advance in the display industry, as they can cover large areas based on screen printing in the production processcompared to a small-molecule OLED utilizing a high vacuum deposition technique-and are flexible enough to realize the production of flexible displays [18][19][20].Since the discovery of poly(phenylenevinylene) in 1990, numerous studies have been undertaken to realize a wide array of colors [21]. Created as part of such endeavors are: blue light-emitting materials such as polyfluorene [22], poly(fluorene-phenothiazine) [23], and polycarbazole [24]; poly(phenylene-vinylene) conductor [25] and other green light-emitting materials; and orange and red lightemitting materials such as poly(fluorene-thiophene) [7], poly(-fluorene-benzothiophene) [26], and poly(fluorene-phenothiazine) conductor [27]. These materials displaying red, green, and blue (RGB) can be used to successfully realize full-color displays.…”